Diyne Coordination Chemistry .4. Synthesis, Molecular-structure, and Protonation Reactions of the Zerovalent Complex [ru(eta-2-phcc-ccph)(co)2(pph3)2]

The reaction of [Ru(CO)2(PPh3)3] with diphenylbutadiyne provides the complex [Ru(eta2-PhC=C-C=CPh)(CO)2(PPh3)2] (1) Which in turn reacts with Bronsted acids, protonation occurring at a coordinated carbon to give 1,4-diphenylbut-1-en-3-yn-2-ylruthenium(II) complexes. Thus [Ru(eta2-PhC=C-C=CPh)(CO)2(PPh3)2] with HPF6 and HCI gives the complexes [Ru-(eta3-PhC=C-C=CHPh)(CO)2(PPh3)2]+(2+) and [Ru(eta1-PhC=C-C=CHPh)CI(CO)2(PPh3)2] (3), respectively, the latter being also the product of the reaction of the former with chloride ion or of the hydridoruthenium complex [RuClH(CO)(PPh3)3] with diphenylbutadiyne followed by carbon monoxide. The Salt [Ru(eta3-PhC=CC=CHPh)(CO)2(PPh3)2]PF6 (2.PF6) was characterized crystallographically [crystals are triclinic of space group P1, Z = 4, in a unit cell of dimensions a = 16.750 (8) angstrom, b = 17.280 (9) angstrom, c = 20.297 (10) angstrom, alpha = 96.10 (4)-degrees, beta = 111.50 (4)-degrees, gamma = 106.29 (4)-degrees, U = 5101 (4) angstrom3], confirming the trihapto coordination which subsequent chemistry, however, indicates is hemilabile. The salt reacts with neutral 2-electron ligands acetonitrile, tert-butylisonitrile, and 2,6-dimethylphenyl isocyanide to afford the monohapto, 1,4-diphenylbut-1-en-3-yn-2-ylderivatives [Ru(eta1-C(C=CPh)=CHPh)(CO)2(L)(PPh3)2]PF6 (L = NCMe (4a.PF6), CN(t)Bu (4b.PF6), CNCrH3Me2-2,6 (4c.PF6)), the acetonitrile ligation in 4a.PF6 being reversible. The neutral azido derivative [Ru{eta1-C(C=CPh)-CHPh}N3(CO)2(PPh3)2] (5) results from reaction of 2.PF6 with sodium azide. Complexes 3 and 2+ react with excess hydrochloric acid to cleave the vinyl ligand and provide [RuCl2(CO)2(PPh3)2].